System of control



Jan. 12 1926. 1,569,409

5. A. STAEGE SYSTEM OF CONTROL Filed May l5 1919 WITNESSES I INVENTOR MVM Sfephen A Sfaega W 6? WeZQ- ATTRNEY Patented Jan. 12, 1926.

UNITED' STATES 1,569,409 PATENT OFFICE.

STEPHEN A. STAEGE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN IA.

SYSTEM OF CONTROL.

Application filed May 15, 1919. Serial No. 287,297.

To all whom it may concern.-

Be it known that I, STEPHEN A. STAEGE, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Control, of which the following is a specification.

My invention relates to systems of control and particularly to systems of control for governing the operation of electric motors.

One object of my invention is to provide I a system of control for an electric motor that shall be equipped with means for effecting a very quick stopping of the motor in case of an emergency or an accident.

In many industries, motor-operated Inachinery is utilized, which, if not stopped 1nstantly at times, such as in case of an accident, will cause serious injury to the operator of the machinery or to other associated machines. Thus, in a rubber mill, sets of rolls are provided for rolling and treating the crude rubber for commercial use and, at times, through carelessness or accident, the hands of the operator feeding the crude rubber to the rolls are drawn between them. In such a case, it is essential that the rotation of the rolls be stopped instantly.

The deceleration of the rolls may be effected by reversing the direction of current flow through the motor which is connected to the rolls. This method is effective for stopping the rotation of the motor but there is always the danger that the motor Wlll immediately start to rotate in the reverse direction unless it is disconnected from the supply circuit at the proper time. If the rolls of the rubber mill should be rotated suddenly in a reverse direction after the hands of the operator had been caught between them, the sudden changing of direction of rotation would be liable to badly mangle the hands of the operator.

In a control system constructed in accordance with my/invention, the motor is decelerated by reversing the direction of current flow through it and means is further provided for automatically disconnecting the motor from the supply circuit in a manner to prevent the rotation of the motor 1n a reverse direction. More specifically, the means provided, in my invention, for preventing the reverse operatlon of the motor,

in case of effecting an emergency stop by A reversing the current flow through it, comprises a differential-gear mechanism, one end portion of which is rotated in accordance with the speed rotation of the rolls and the other end portion of which is rotated at a constant speed by any auxiliary source of power. The central portion of the differential-gear mechanism, which rotates in a direction determined by the relative speeds of the two end portions, controls a switch which effects the disconnection of the motor from the supply circuit in a manner to prevent any reverse operation of the motor. Thus, the motor is decelerated by reversing the direction of the current flow throu h it, and, when the speed of the motor is r uced to a predetermined point, the central portion of the difl'erential-gear mechanism changes its direction of rotation and opens the switch which effects the disconnection of the motor from the supply circuit.

In the accompanying drawings, Figure 1 1s a diagrammatic view of a control system constructed in accordance with m invention, and Figs. 2 and 3 are, respectively, front and side elevational views of the differential-gear mechanism which automatically disconnects the motor from the supply circuit.

Referring to the drawing, rolls 1 and 2 are connected together by means of gear wheels 3 and are rotatably journalled in any suitable bearin brackets or standards 4. A motor 5, suc for example, as a three phase induction motor, is connected to the rolls by means of a set of gear wheels 6 and is adapted to operate the rolls in a forward and in a reverse direction.

Two reversing switches 7 and 8, res ectively comprising energizing coils 9 and 10, and switch members 11 and 12, are provided for connecting the motor am a three-phase supply circuit comprising conductors 13, 14 and 15, the switch 8 serving to connect the motor to the supply circuit for operating the rolls in a forward direction and the switch 7 serving to connect the motor to the supply circuit for operating the rolls in a reverse direction.

Adjacent to the rolls, in any convenient. location, is disposed a switch 16 for selectively operating the switches 7 and 8. The switch 16 embodies a contact member 17, which is moved into engagement with a stationary contact member 18 when it is desired to operate the rolls in a forward direction, and a contact member 19, which is moved into engagement with the stationary contact member 20 when it is desired either to operate the rolls in a reverse direction or to quickly decelerate the motor. When the contact members 19 and 20 are in engagement, the coil 9 of the switch 7 is connected across theconductors 21 and 22 of an auxiliary supply circuit and, when the contact members 17 and 18 are in engagement with each other, the coil 10 of the switch 8 is connected across the supply conductors 21 and 22. The movable contact members 17 and 19 are mounted on a .pivotally mounted contact arm 23 which is controlled by the operator of the rolls.

A differential-gear mechanism 25, which is illustrated in Figs. 2 and 3 of the drawing, is provided for opening the energizing circuit of the switch 7 to disconnect the motor from the supply circuit in case the motor is decelerated by reversing the direction of current flow through it. The differential-gear mechanism comprises an end portion 26, which is rotated in accordance with the speed of rotation of the rolls 1 and 2, a second end portion 27, which is rotated at a constant speed by any auxlhary source of power, such as the motor 28, and a central portion 29, which is rotated at a speed and in a direction determined by the relative rotation of the two end portions 26 and27 for selectively operatinga switch 30. The three members 26, 27 and 29 of the differential-gear mechanism are rotatably mounted upon a suitable shaft 31.

The end portion 26 is provided with bevel gear teeth 32 on one side thereof for engaging bevel pinions 33, which are mounted in the central portion 29, and is directly connected to a shaft 34 of the roll 2 in any suitable manner, such as by a flexible connector 35. The end portion 27 is provided with bevel gear teeth 36 on one side thereof for engaging the bevel pinions 33 and gear teeth v37 on the periphery thereof for engaging a pinion 39 that is mounted on the armature shaft-of the motor 28.

- The central portion 29 of the difierentialgear mechanism embodies a member 40 having the pinions 33 rotatably mounted therein in amanner to engage the bevel teeth of the end portions 26 and 27 and a strap member 41, which is held in frictional engagement with the member 40. The strap member 41 is held in engagement with the member 40 by means of a bolt 42, which passes through the two end portions of the strap .41, and a spring 43 which is located between one end portion of the strap 41 and the head of the bolt 42. The switch 30 embodies a stationary contact member 44 and a movable contact member 45 which is mounted in any suitable manner upon the strap 41.

Assuming the contact members 17 and 18 to be in engagement for operating the switch 8, the motor 5 is connected across the supply conductors 13, 14 and 15 for operating the rolls 1 and 2 in a forward direction. Moreover, it is assumed that the motor 28 is connected to any suitable source of power and is operated at such speed that the end portion 27 of the differential-gear mechanism rotates at a considerably less speed than the end portion 26 which is connected to the set of rolls 1 and 2. Thus, the main portion 26, if rotating at a higher speed than the end portion 27, will control the central portion 29 of the differential-gear mechanism and will give it a movement of rotation in a counter-clockwise direction such as to maintain the contact members 44 and 45, of the switch member 30 in engagementwith each other.

In case of an accident, the switch 16 is reversed to disengage the contact members 17 and 18 and to engage the contact members 19 and 20 and thus de-energize the switch 8 and operate the switch 9 to reverse the direction of current flow through the motor 5. The motor 5 and the rolls 1 and 2 are rapidly decelerated and, when the speed of rotation of the end portion 27 of the differential-gear mechanism 25 is greater than the speed of rotation of the end portion 26, the end portion 27 governs the operation of the central portion 29. Accordingly, the central portion 29 effects a movement of rotation in a clockwise direction to open the switch 30. The switch 30, which is included in the energizing circuit of the reversing switch 7, de-en'ergizes the switch 7 and thus disconnects the motor 5 from the supply circuit and, consequently, insures'the motor 5 and the rolls 1 and 2 against rotation in a reverse direction.

By adjust-ing the speed of rotation of the end portion 27 it is apparent, that the differential-gear mechanism will operate to open the switch 30 at any desired s d of rotation of the rolls 1 and 2. Pre erably,

- the switch .30 is opened when the rolls 1 and 2 are rotatedvery close to zero speed. In case it is desired to operate the rolls in a reverse direction, independent of the safety device, the auxiliary switch 48 is provided made within the spirit and scope of my invention and I desire, therefore that only such limitations shall be imposed dicated in the appended claims.

I claim as my invention:

1. In a control system for a set of rolls, a main electric motor for operating said rolls in a forward and in a reverse direction, current reversing means for the main motor, an auxiliary motor, and means comprising a differential gear jointly controlled by said rolls and the auxiliary motor for deenergizing the main motor and for rendering the current reversing means ineffective after a reversal of motor current.

2. In a control system for a plurality of rolls, the combination with a supply circuit, a main motor adapted to operate said rolls, two switches for connecting the motor to the supply circuit and for controlling the direction of motor current to provide reversal thereof, and a master switch for selectively energizing said switches, of an auxiliary motor, a differential gear having members thereof respectively rotated by said main motor and said auxiliary motor, and means controlled by the planetary members of the diiferential gear for opening the controlling circuit of said master switch in case the speed of said rolls upon a reversal of current falls below a predetermined value, corresponding to the speed of the auxiliary motor.

3. In a control system for a set of fabrictreating rolls, a polyphase supply circuit, a polyphase motor for operating the rolls in as are in a forward and in a reverse direction, a pair of multi-pole switches for alternatively connecting said motor to said supply circuit for forward or reverse drive, and means differentially connected to said rolls for deenergizing the reverse drive switch to efiect stoppa e of the motor and the rolls when the speed t ereof reaches a relatively low value.

4. In a control system for a set of fabrictreatin rolls, a three-phase supply circuit, a three-p ase induction motor for operating the rolls, two electrically-operated three-pole switches for connecting said motor to said supply circuit for forward or reverse drive, a manually-operated switch for selectively energizing sald switches, an auxiliary constant-speed motor, a differential device having members thereof respectively rotated by said induction motor and said auxiliary motor, and a switching device controlled by the planetar portion of said device for deenergizing t e reverse drive switch to effect stoppa e of the motor and the rolls when the speed t ereof reaches a relatively low value.

5. In a control system for a set of fabrictreating rolls, a supply circuit, a motor for operating said rolls, switches for effecting reversal of the current throu h said motor to efl'ect dynamic braking an means difiersubscribed my name this 3rd day of May,

STEPHEN A. STAEGE. 

